Judging by demand, many natural perfumes are available in totally inadequate quantities. For example, 5,000 kg of rose blossoms are required to produce 1 kg of rose oil. The consequences are a seriously limited annual world production and a high price. Accordingly, it is clear that the perfume industry has a constant need for new perfumes with interesting notes in order to add to the range of naturally available perfumes, to make the necessary adaptations to changing fashion trends and to be able to cover the constantly increasing demand for improvements in the odor of products of everyday use, such as cosmetics and cleaners.
In addition, there is generally a constant demand for synthetic perfumes which can be favorably produced in a consistent quality and which have desirable olfactory properties, i.e. pleasant, close-to-nature andxe2x80x94qualitativelyxe2x80x94novel odor profiles of sufficient intensity, and which are capable of favorably influencing the smell of cosmetic products and consumer goods. In other words, there is a constant need for compounds which have characteristic new odor profiles and, at the same time, high staying power, intensity of odor and emanative power.
The present invention relates, in general, to carbonyl compounds with a particular structure, and to a process for their production and their use as perfumes.
It has been found that compounds corresponding to general formula (I) meet the requirements stated above in every respect and may advantageously be used as perfumes with differently nuanced odor notes characterized by high staying power.
In a first embodiment, the present invention relates to carbonyl compounds corresponding to general formula (I): 
in which R1 is hydrogen or a C1-5 alkyl group, R2 and R3 independently of one another represent hydrogen or a C1-3 alkyl group, a Cxe2x95x90C double bond is present in one of the positions C-1/C-2, C-2/C-3 or C-1/C-6 and R4 is either hydrogen orxe2x80x94if the Cxe2x95x90C double bond is in the C-2/C-3 positionxe2x80x94is hydrogen or a C1-3 alkyl group.
2-(2xe2x80x2-n-hexylcyclopent-2xe2x80x2-en-1xe2x80x2-yl)-acetaldehyde, 2-(2xe2x80x2-n-hexylcyclopent-2xe2x80x2-en-1xe2x80x2-yl)-propionaldehyde and (2-n-hexylcyclopent-2-en-1 -yl)-acetone are most particularly preferred.
The compounds corresponding to formula (I) may be prepared by any of the methods known to the preparative organic chemist. According to the invention, however, they are prepared in particular from special allyl alcohols, the 2-alkylcyclopent-2-en-1-ols, which may optionally contain another alkyl group in the 3-position and which, when reacted with special vinyl ethers, give intermediate products that are accessible to [3,3]-sigmatropic rearrangements. In the case of the rearrangement products, the Cxe2x95x90C double bond formed primarily in the five-membered ring may be subsequently shifted towards the carbonyl group.
2-Alkylcyclopent-2-en-1-onesxe2x80x94products generally obtainable commercially under such names as isojasmone, sedamon, cis-jasmone, dijasmone, dihydrojasmone or dihydroisojasmone or by aldol condensation of cyclopentanone with various aldehydesxe2x80x94can be selectively reduced to the corresponding allyl alcohols, the 2-alkylcyclopent-2-en-1-ols, with complex hydrides such as, for example, alkali metal borohydrides or aluminium hydrides, or by Meerwein-Ponndorf reduction with aluminium alcoholates.
The present invention also relates to a process for the production of carbonyl compounds (I) in which alkyl cyclopentenols corresponding to general formula (II): 
in which R1 and R4 are as defined above, are reacted with vinyl ethers corresponding to general formula (III): 
in which R2 and R3 are as defined above. The xe2x80x9cAlkylxe2x80x9d moiety in formula (III) is methyl, ethyl, propyl, C4-10 alkyl and cycloalkyl.
Examples of suitable vinyl ethers are ethyl vinyl ether, 2-methoxypropene, 1-propenyl ethyl ether, 2-propenyl ethyl ether, cyclohexyl vinyl ether.
The compounds (I) are distinguished by a pronounced aldehydic character to their odor with intensive green and fruit notes.
In perfume compositions, the compounds (I) strengthen harmony, emanation and also staying power, the quantities used being adapted to the particular perfume note required taking the other ingredients of the composition into account.
The fact that the carbonyl compounds (I) have aldehydic green-fruity notes was not foreseeable and, hence, is further confirmation of the general experience that the olfactory properties of known perfumes do not allow any definitive conclusions to be drawn as to the properties of structurally related compounds because neither the mechanism of odor perception nor the influence of chemical structure on odor perception has been sufficiently researched, so that it is not normally possible to predict whether modifications to the structure of known perfumes will in fact lead to changes in their olfactory properties or whether these changes will be positive or negative.
Accordingly, the present invention also relates to the use of the compounds (I) as perfumes.
By virtue of their odor profile, the compounds corresponding to formula (I) are also particularly suitable for modifying and enhancing known compositions. Particular emphasis is placed on their extreme intensity of odor which contributes quite generally towards refining the composition.
The compounds corresponding to formula (I) may be combined with many known perfume ingredients, for example other perfumes of natural, synthetic or partly synthetic origin, essential oils and plant extracts. The range of natural fragrances can thus include both high-volatility and also medium-volatility and low-volatility components while the range of synthetic perfumes may include representatives of virtually every class of compounds. Examples are:
(a) natural products, such as tree moss absolue, basil oil, citrus oils, such as bergamot oil, mandarin oil, etc., mastix absolue, myrtle oil, palmarosa oil, patchouli oil, petitgrain oil, wormwood oil, myrrh oil, olibanum oil
(b) alcohols, such as farnesol, geraniol, linalool, nerol, phenylethyl alcohol, rhodinol, cinnamic alcohol, sandalore [3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)-pentan-2-ol], sandela [3-isocamphyl-(5)-cyclohexanol]
(c) aldehydes, such as citral, Helional(copyright), xcex1-hexyl cinnamaldehyde, hydroxycitronellal, Lilial(copyright) [p-tert.butyl-xcex1-methyldihydrocinnamalde-hyde], methylnonyl acetaldehyde
(d) ketones, such as allylionone, xcex1-ionone, xcex2-ionone, isoraldein, methyl ionone
(e) esters, such as allylphenoxyacetate, benzyl salicylate, cinnamyl propionate, citronellyl acetate, citronellyl ethoxylate, decyl acetate, dimethylbenzyl carbinyl acetate, ethyl acetoacetate, hexenyl isobuty-rate, linalyl acetate, methyl dihydrojasmonate, vetiveryl acetate, cyclohexyl salicylate
(f) lactones, such as gamma-undecalactone, 1-oxaspiro[4.4]-nonan-2-one and various other components often used in perfumery, such as musk, indole, p-methan-8-thiol-3-one, methyl eugenol, Ambroxan.
It is also remarkable how the compounds corresponding to formula (I) round off and harmonize the odor notes of a broad range of known compositions without unpleasantly dominating them in any way. 2-(2xe2x80x2-n-hexylcyclopent-2xe2x80x2-en-1xe2x80x2-yl)-antaldehyde is particularly emphasized in this regard.
The compounds according to the invention contain chirality centers so that they may exist in various spatial forms. The compounds according to the invention accumulate as mixtures of the corresponding isomers in the course of typical syntheses and are used in this form as perfumes/fragrances.
The compounds according to the invention or mixtures thereof may be used in perfume compositions in quantities of 1 to 70% by weight, based on the mixture as a whole. Mixtures of compounds (I) according to the invention and compositions of this type may be used both for perfuming cosmetic preparations, such as lotions, creams, shampoos, soaps, emollients, powders, aerosols, toothpastes, mouthwashes, deodorants, and also in alcohol-based perfumery (for example colognes, toilet waters, extracts). The compounds according to the invention or mixtures thereof may also be used for perfuming commercial products, such as detergents, fabric softeners and textile treatment preparations. For perfuming these various products, the compositions are added in an olfactorily effective quantity, more particularly in a concentration of 0.05 to 2% by weight, based on the product as a whole. However, these values are not intended to represent limits because the experienced perfumer can also obtain effects with even lower concentrations or can build up new complexes with even higher doses.